For many decades separation, classification, sifting and dewatering of fragmented stocks of hard material such as crushed rock, aggregate, coal, sand and the like have been accomplished by shaker screen boxes having screen bodies made up either of coarse-woven steel or other metal netting, or of relatively thin sheet metal material provided with sieve openings arranged in predetermined sequence or manner. The abrasion and wear from hard material striking the charging surfaces of such screens, as well as the impact, tumbling and flow of hard material on such surfaces, has caused rather rapid deterioration of the metal material. Further, corrosion and deformation of the material from impact has shortened the life of such screens. The din and noise from the charging of such screens and the bouncing and tumbling of hard material thereon have been a source of noise pollution. In the last fifteen years several efforts have been made to lengthen the life of such metal screens by applying coatings of somewhat flexible elastic or elastomer material and in several instances whole screen bodies or sections of screen bodies involving a multiplicity of sizing apertures have been employed. Some of these have been supported and reinforced by an underlying mesh of steel, wires or the equivalent. Complicated molding processes have been required for such prior art shaker screens and because the manufacturer is required to make and have available screens having mesh sizes, sometimes square, sometimes round, sometimes elongate, and in as many as a hundred sizes, the investment or original cost of such processing, and in many instances the mold has been extremely high and prohibitive. Some prior structures have employed laminations of plastic or elastic sheets vulcanized to metal sheets and some have employed two or more plies of elastomer sheets of large size, properly punched or apertured for the sizing required.
It is a main object of the instant invention to provide an inexpensive, highly efficient elastomer, sectional screen unit readily connectible with a multiplicity of such units in directions both longitudinally and transversely of the direction of flow of fragmented, hardstock materials to constitute collectively a full shaker screen. The embodiments of this invention are particularly adapted for sizing, sifting and dewatering fragmented hard-stock materials of the smaller sizes and preferably each unit is constructed integrally to provide a substantial number of sizing apertures with a minimal requirement of intervening solid material. With the employment of my invention, substantial economy is achieved in the original installation, in the cost of machinery or apparatus for either molding or die-cutting of the novel sectional units, as contrasted with the production of any known prior art sectional units.
One form of this invention is disclosed and illustrated in my U.S. Pat. No. 3,943,054 issued Mar. 9, 1976. Additional embodiments of the invention are herein disclosed and illustrated which provide for more efficient and simple interconnection of a multiplicity of the screen units and minimize mounting and support of the units while still affording independent hinge action of the screen units when interconnected with other units of the complete shaker screen.